int|null nat = 6

let nat as int

int foo = nat + 12
println(foo)


int|[i8] a = 24
if (true) {
    let a as int

    // x a = [3, 4, 5], a 此时是一个 int 类型不能赋值数组
    // 在一个临时作用域中让 a 作为 int 类型
    println(a + 12)
}

// a 此时是一个 union 类型，所以不能作为 literal 的类型参考
a = [3 as i8, 4, 5]
print(a is int, a is null, a is [i8], '\n')

[i8] b = [3, 4, 5]
println(b.len)

